Replacement of analog circuit components such as NCOs (numerically controlled oscillators) and/or PLLs (phase-locked-loop) with digital circuits (e.g. digital logic circuits) may be an area of interest in various applications, e.g. in RF (radio frequency) systems.
Whilst digital circuits have been decreasing in size, analog circuit components have not followed digital circuits in their shrink-factor. Furthermore, functionalities provided by digital circuits have improved at a greater pace than have analog circuit components. Accordingly, it may be desirable to investigate circuit arrangements that may include replacement of analog circuit blocks with digital blocks having small form factors and/or enhanced functionality. For example, currently used NCOs may have technical limitations in its frequency-range and modulation bandwidth, which could be resolved by means of digital circuits. Besides enhanced functionality, replacement of some analog circuit blocks with digital blocks may yield a mixed-signal circuit that may be enable multi-signal sourcing (namely, using both analog and digital signals) and easy migration to future technology nodes with close to digital shrink factors. Even further, digital implementations may allow reproducibility and potential for extra functionality, which may not be realized in the analog domain. Examples include digital assisted calibration and/or digital adjustments for yield improvements.
Whilst replacement of some analog circuit with digital circuits may be desirable, a challenge for mixed-signal implementations (e.g. in RF applications) may be compliance with stringent requirements regarding the circuit's noise levels and SFDR (spurious-free dynamic range), especially in light of future technology nodes. It may be desirable to provide new circuits that may meet requirements for noise level and SFDR.